Hantavirus

Murine viruses.

Can be caused by at least 24 viruses

Since 1993, a total of 728 cases have been reported.

Reportable infection with about a 36% case fatality rate.

Transmission occurs by inhaled viral particles of rodent excreta.

Rarely acquired by the handling of rodents in laboratories.

Humans generally become infected through the inhalation  of aerosolized secreta  or excreta containing infectious virions originating from a rodent reservoir.

Primarily a disease of adults with <7% reported in children less than 17 years of age.

Hantavirus pulmonary syndrome with severe pneumonia may occur.

2-10 day prodromal period with nonspecific symptoms and a late acute respiratory phase which begins abruptly.

Most cases reported in the southwestern U.S.

Leucocytosis and thrombocytopenia typically seen.

Antiviral agents not effective.

Management is supportive care.

Low cardiac index and stroke volume are important causes of death in the Hantavirus pulmonary syndrome.

Transmitted from rodent hosts via inhalation of infectious aerosols of rodent excretions or direct inoculation into broken skin.

Sin Nombre virus is the most common cause of the Hantavirus pulmonary syndrome, and the deer mouse (Peromyscus maniculatus)is its reservoir.

Of the Hantavirus pulmonary syndrome cases reported by the CDC 43% arose from domestic exposure, 5% from recreational activities, and 8% from occupational exposure, with 44% without clear exposure history.

Exposure to Sin Nombre eight virus can occur to inhalation of aerosol particles from contaminated feces, urine, or saliva, or to direct inoculation from an animal bite.

Sin Nombre human-to-human transmission has not been reported.

Humans typically get hantavirus infection when urine or feces from infected rodents is aerolized, as by sweeping, and inhaled by susceptible individuals.

The Hantavirus is viable for 9 to 15 days in the environment.

The incubation period after exposure ranges from 9-33 days with a median 14-17 days.

The 2 to 1 male predominance felt to be secondary to increased occupational exposure.

The incubation period is followed by a prodromal phase that lasts 3-5 days.

The prodromal phase is characterized by a high fever, myalgias, malaise, severe headaches with neck pain, abdominal pain, associated with nausea vomiting and occasionally diarrhea.

Severe leukocytosis and thrombocytopenia also develop.

There is typically minimal or no involvement of the liver or kidneys.

The prodromal phase is followed by an abrupt progression to the cardiopulmonary phase, characterized by cough with non-purulent secretions and dyspnea with severe respiratory distress.

Myocardial depression and increased peripheral vascular resistance is also common.

Recommended trapping rodents and preventing exposure to potentially infected rodent species.

Diagnosis of acute infections is based on detection of virus specific IgM.

Antibodies to IgM and IgG  against the Sin Nombre virus develop rapidly during the prodromal phase  and are almost universally present during the cardio pulmonary phase.

Serologic testing for hanta virus specific IgM is the most commonly perform diagnostic test, because all infected person to have antivirus specific IgM at the onset of clinical symptoms.

Hanta specific IgG is often present in the blood after onset of illness and can persist for months to years.

Laboratory findings include thrombocytopenia, atypical lymphocytosis and hemoconcentration.

Lymphoblasts may be seen in the Hantavirus pulmonary syndrome.

Liver function elevations commonly seen with the Hantavirus pulmonary syndrome.

Pulmonary edema that is present is mediated by T-cell response to the viral infection of the microvascular pulmonary endothelial cells.

Cardiogenic shock is the usual cause of death.

Diagnosis is usually clinical with the patient manifesting fever, hypoxemia, bilateral interstitial edema and evidence of idiopathic noncardiogenic pulmonary edema with ELISA testing to detect IgM antibodies to the Sin Nombre virus or other hantaviruses.

Mortality rate in the hantavirus pulmonary syndrome ranges from 36-76%, but lower rates reported more recently as the diagnosis is being recognized earlier and the use of improved supportive care being implemented sooner.